Panel molded electronic assemblies with integral terminals

ABSTRACT

Encapsulated electronic modules having complex contact structures may be formed by encapsulating panels containing a substrate comprising pluralities of electronic modules delineated by cut lines and having conductive interconnects buried within terminal holes and other holes drilled in the panel within the boundaries of the cut lines. Slots may be cut in the panel along the cut lines. The interior of the holes, as well as surfaces within the slots and on the surfaces of the panel may be metallized, e.g. by a series of processes including plating. Terminals may be inserted into the terminal holes and connected to conductive features or plating within the holes. A conductive element may be provided on the substrate to connect to a terminal. Alternatively solder may be dispensed into the holes for surface mounting.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. patent application Ser. No. 16/218,395,filed on Dec. 12, 2018, the entire disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to the field of encapsulated electronicassemblies, including encapsulated power converters, and moreparticularly to providing externally accessible connection terminalsthat provide a conductive path to elements within the encapsulatedassembly.

BACKGROUND

An encapsulated electronic module, such as an electronic power convertermodule for example, may comprise a printed circuit assembly over-moldedwith an encapsulant to form some or all of the package and exteriorstructure or surfaces of the module. Encapsulation in this manner mayaid in conducting heat out of the over-molded components, i.e.,components that are mounted on the printed circuit assembly and coveredwith encapsulant. It is necessary to provide means for making electricalconnections between the internal printed circuit assembly and externalcircuitry (e.g. an external printed circuit board; a socket). There aremany known ways to make such connections, including, but not limited to,lead frames, pins, conductive terminals and flexible wire leads.

SUMMARY

In general, in one aspect, a method of forming electronic modules isprovided. The method includes: assembling an electronic module includinga multilayer printed circuit board (“PCB”) having a plurality ofconductive layers, a first plurality of electronic components mounted toa first surface of the PCB, and a first layer of cured encapsulantcovering the components and the surface of the PCB, the first layer ofcured encapsulant forming a first exterior surface of the module, theelectronic module including one or more conductive features buriedbeneath the first exterior surface; selectively forming one or moreterminal holes in the first exterior surface through the first layer atpredetermined locations within perimeter boundaries of the electronicmodule, exposing within the one or more terminal holes respectiveportions of the one or more conductive features; inserting a conductiveterminal into each of the one or more terminal holes; and forming anelectrical connection between the conductive terminal and the respectiveportions of the one or more conductive features exposed within each ofthe one or more terminal holes.

Implementations of the aspect can include one or more of the followingfeatures. The method can further include selectively forming one or moreconductive metal layers on the first exterior surface and on a sidewallsurface within each of selected terminal holes in electrical contactwith the respective portions of the one or more conductive featuresexposed within the selected terminal holes. The one or more conductivefeatures further can include at least one of the conductive layers, atleast one of the terminal holes are formed through a portion of the PCB,and the respective portions of the one or more conductive featuresinclude edges of the at least one of the conductive layers. Forming anelectrical connection can include, for each selected terminal hole,soldering the respective conductive terminal to the conductive metallayer within the selected terminal hole or the respective portions ofthe one or more conductive features exposed within the selected terminalhole, or both. Each respective conductive terminal can include acolumnar portion that extends beyond the first exterior surface of theelectronic module and can be adapted to engage with a through hole in asecond printed circuit board external to the electronic module. Eachrespective conductive terminal can include a threaded hole adapted toaccept a threaded fastener.

Forming an electrical connection for selected terminal holes can includeforming a pressure fit between the respective conductive terminal andthe respective portions of the one or more conductive features exposedwithin the selected terminal holes. The selected terminal holes each canhave a circular cross-section and each respective terminal can include aportion lying within each selected terminal hole having indentationsproviding gaps between the portion of the terminal and the sidewallsurface of the hole. The indentations can be adapted to allow gases toescape from the selected holes during the soldering. The indentationscan include features adapted to resist rotation of the terminal in theterminal hole. Assembling the electronic module can include mounting atleast one conductive component to the PCB, the at least one conductivecomponent can be covered by the first layer of cured encapsulant, andforming the one or more terminal holes can include exposing theconductive component in a respective one of the terminal holes. Theconductive component can include a hole feature covered by the firstlayer of cured encapsulant and approximately aligned with a location ofthe respective one of the terminal holes, and the respective one of theterminal holes can expose the hole feature.

Forming one or more conductive metal layers can include patterning toproduce a metal pad on an external surface of the electronic modulesurrounding the terminal holes, the metal forming the pad can becontinuous with the metal extending into the at least one terminal hole,and the metal pad can provide an electrical contact on the externalsurface connected to the one or more exposed features. Forming anelectrical connection can include soldering the conductive terminal tothe metal within the selected terminal hole or the pad on the externalsurface, or both. The method can further include selectively forming oneor more conductive metal layers on a sidewall surface within each ofselected terminal holes in electrical contact with the respectiveportions of the one or more conductive features exposed within theselected terminal holes.

The method can further include: selectively forming one or more mountingholes in the first exterior surface through the first layer atpredetermined locations within perimeter boundaries of the electronicmodule, each mounting hole intersecting a respective second set of theconductive features to expose respective portions of the respectivesecond set of conductive features in the respective mounting hole. Themethod can further include: selectively forming one or more conductivemetal layers on the first external surface and on a sidewall surfacewithin each of selected mounting holes in electrical contact with theexposed respective portions of the respective second set of conductivefeatures in the respective mounting hole to form a conductive metalmounting pad on the first exterior surface surrounding the respectivemounting hole, the metal mounting pad being continuous with the one ormore conductive metal layers on the interior surface of the respectivemounting hole and providing an electrical contact on the first exteriorsurface connected to the exposed respective portions of the respectivesecond set of the conductive features.

The method can further include patterning the one or more metal layerson the first exterior surface to form a metal shield electricallyconnected to at least one of the metal mounting pads and covering atleast 25 percent of the first exterior surface. The metal shield cancover at least 50% of the exterior module surface and connect aplurality of the mounting holes. At least one of the mounting holes canextend completely through the module. Assembling the electronic modulecan include providing a PCB panel, mounting a plurality of electroniccomponents to first and second surfaces of the PCB panel, encapsulatingthe PCB panel and electronic components to form an encapsulated panel,the encapsulated panel comprising a plurality of the electronic modules,and cutting the encapsulated panel to singulate the electronic modules.In some examples, the cutting step can be performed after the steps offorming the terminal holes and forming one or more conductive metallayers. In some examples, the cutting can be performed after the step ofinserting the conductive terminal. In some examples, the cutting can beperformed before the step of inserting the conductive terminal.Selectively forming one or more terminal holes can further include usinga laser, and the one or more conductive features can include aconductive feature on the first surface of the PCB. The laser caninclude a wavelength that removes encapsulant at a rate that is at leastan order of magnitude greater than a rate at which material is removedfrom the conductive feature on the first surface of the PCB. The one ormore holes can be limited in depth by the conductive feature on thefirst surface of the PCB.

In general, in another aspect, apparatus includes an electronic moduleincluding a multilayer printed circuit board (“PCB”) having a pluralityof conductive layers, a first plurality of electronic components mountedto a first surface of the PCB, and a first layer of cured encapsulantcovering the first plurality of components and the first surface of thePCB, the first layer of cured encapsulant forming a first exteriormodule surface. The apparatus includes one or more conductive featuresburied beneath the first exterior module surface; and one or moreterminal holes formed in the first layer of cured encapsulant, eachterminal hole intersecting a respective set of the conductive featuresto expose respective portions of the selected set of the conductivefeatures and having a respective conductive terminal within the terminalhole and electrically connected to the respective portions of therespective set of conductive features.

Implementations of the aspect can include one or more of the followingfeatures. The apparatus can include a conductive metal layer formed onan interior surface of selected terminal holes in contact with therespective portions of the respective set of conductive features withinthe respective terminal hole. The selected set of conductive featurescan include one or more of the conductive layers of the PCB, eachselected terminal hole can be formed through at least a portion of thePCB, and the respective portions of the one or more conductive featurescan include edges of the one or more conductive layers. The apparatuscan further include a conductive metal pad formed on the first exteriormodule surface surrounding one or more of the selected terminal holes,the metal pad can be continuous with the conductive metal layer on theinterior surface of the one or more of the selected terminal holes andprovide an electrical contact on the first exterior module surfaceconnected to the one or more exposed features within the respectiveterminal hole. The apparatus can further include a solder connectionbetween a portion of the conductive terminal and the conductive metallayer on the interior surface of the one or more selected terminalholes. The apparatus can further include a solder connection between aportion of the conductive terminal the conductive metal pad.

The apparatus can further include one or more mounting holes formed inthe first layer of cured encapsulant, each mounting hole can intersect arespective second set of the conductive features to expose respectiveportions of the respective second set of conductive features in therespective mounting hole. Each mounting hole can have a conductive metallayer formed on an interior surface of the respective mounting hole incontact with the exposed respective portions of the respective secondset of conductive features within the respective mounting hole and aconductive metal mounting pad formed on the exterior module surfacesurrounding the respective mounting hole, and the metal mounting pad canbe continuous with the conductive metal layer on the interior surface ofthe respective mounting hole and providing an electrical contact on theexterior module surface connected to the exposed respective portions ofthe respective second set of the conductive features. The metal mountingpad can further include a conductive metal shield covering a at least 25percent of the exterior module surface. The conductive shield can coverat least 50 percent of the exterior module surface and connect aplurality of the mounting holes. The mounting holes can extendcompletely through the electronic module. The electronic module canfurther include a second set of electronic components mounted to asecond surface of the PCB, a second layer of cured encapsulant can coverthe second set of components and the second surface of the PCB, and thesecond layer of cured encapsulant can form a second exterior modulesurface.

The apparatus can further include a conductive metal layer formed on aninterior surface of each of selected terminal holes in contact with therespective portions of the respective set of conductive features withinthe respective terminal hole. The selected set of conductive featurescan include one or more of the conductive layers of the PCB, eachselected terminal hole can be formed through at least a portion of thePCB, and the respective portions of the one or more conductive featurescan include edges of the one or more conductive layers. The apparatuscan further include a conductive metal pad formed on the first exteriormodule surface surrounding one or more of the selected terminal holes,and the metal pad can be continuous with the conductive metal layer onthe interior surface of the one or more of the selected terminal holesand provide an electrical contact on the first exterior module surfaceconnected to the one or more exposed features within the respectiveterminal hole. The apparatus can further include a solder connectionbetween a portion of the conductive terminal and the conductive metallayer on the interior surface of the one or more selected terminalholes. The apparatus can further include a solder connection between aportion of the conductive terminal and the conductive metal pad.

The apparatus can further include one or more mounting holes formed inthe first and second layers of cured encapsulant and PCB, each mountinghole can extend completely through the module and intersect a respectivesecond set of the conductive features to expose respective portions ofthe respective second set of conductive features in the respectivemounting hole. Each mounting hole can have a conductive metal layerformed on an interior surface of the respective mounting hole in contactwith the exposed respective portions of the respective second set ofconductive features within the respective mounting hole and a conductivemetal mounting pad formed on one or both of the first and secondexterior module surfaces surrounding the respective mounting hole, andthe metal mounting pad can be continuous with the conductive metal layeron the interior surface of the respective mounting hole and provide anelectrical contact on the exterior module surface connected to theexposed respective portions of the respective second set of theconductive features. The metal mounting pad can further include aconductive metal shield covering a at least 25 percent of one or both ofthe first and second exterior module surfaces. The conductive shield cancover at least 50 percent of both of the first and second exteriormodule surfaces and electrically connect to a plurality of the mountingholes. The selected set of conductive features can include a conductivetrace on a surface of the PCB, each selected terminal hole can belimited in depth to the surface of the PCB, and the respective portionsof the one or more conductive features can include a surface of theconductive trace at a bottom of each terminal hole.

In another general aspect, a method of forming modular circuitassemblies is provided. The method includes: assembling an encapsulatedpanel including a multilayer printed circuit board (“PCB”) having aplurality of conductive layers, a first plurality of electroniccomponents mounted to a first surface of the PCB, and a first layer ofcured encapsulant covering the first plurality of electronic componentsand the surface of the PCB, the first layer of cured encapsulant forminga first exterior surface of the encapsulated panel, the encapsulatedpanel comprising a plurality of unsingulated electronic modules, eachmodule having perimeter boundaries defined by one or more predeterminedcut lines and one or more conductive features buried beneath the firstexterior surface; selectively forming a plurality of terminal holes inthe first exterior surface of the panel through the first layer atpredetermined locations within the perimeter boundaries of eachelectronic module, each terminal hole being spaced apart from the cutlines and exposing within the hole a respective conductive feature;selectively forming one or more conductive metal layers on the firstexterior surface of the panel including within the plurality of terminalholes, the one or more conductive metal layers within each terminal holebeing in electrical contact with the respective conductive feature;patterning the one or more conductive metal layers on the exteriorsurface, to form a plurality of electrical contacts on the exteriorsurface of the panel electrically isolated from at least one otherelectrical contact in the plurality of electrical contacts; and cuttingthe panel along the one or more cut lines to singulate the plurality ofelectronic modules, each singulated electronic module having arespective plurality of the electrical contacts formed on the exteriorsurface of the module.

Implementations of the aspect can include one or more of the followingfeatures. The method can further include selectively dispensing solderto each of the terminal holes, at least partially filling each terminalhole with solder. The method can further include applying a compressiveforce to the dispensed solder to establish a predetermined uniformheight relative to the first exterior surface. The method can furtherinclude selectively dispensing a curable compound to each of the ofterminal holes, at least partially filling each terminal hole with thecurable compound, curing the compound; and selectively dispensing solderto each of the terminal holes, at least partially further filling eachterminal hole with solder. The method can further include applying acompressive force to the dispensed solder to establish a predetermineduniform height relative to the first exterior surface. Selectivelyforming a plurality of terminal holes can further include using a laser;the respective conductive feature can include a conductive trace on thefirst surface of the PCB; the laser can include a wavelength thatremoves encapsulant at a rate that is at least an order of magnitudegreater than a rate at which material would be removed from theconductive trace; and the plurality of terminal holes can be formed at adepth that is limited by the respective conductive trace on the surfaceof the PCB.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an isometric view of an electronic module.

FIG. 2 is an exploded view showing terminals prior to insertion inplated holes.

FIG. 3 shows an isometric view of an encapsulated panel comprisingseveral electronic modules included in regions defined by cut lines.

FIG. 4 shows the panel of FIG. 3 comprising slots cut along the cutlines.

FIG. 5 shows the panel of FIG. 4 after metallization.

FIG. 6 shows a portion of the panel of FIG. 5 after singulation.

FIG. 7A shows a cross section of a terminal hole in an electronic modulethat passes entirely through an internal substrate.

FIG. 7B shows a cross section of a terminal hole in an electronic modulethat does not penetrate an internal substrate.

FIG. 7C shows a cross section of terminal holes in an electronic modulethat pass partially and completely through an internal substrate.

FIGS. 8A and 8B are cross-sectional views of a terminal soldered into aplated hole.

FIGS. 9A and 9B are cross-sectional views showing both soldered andpress-fit terminals in plated holes.

FIG. 10 shows a conductive feature on a surface of the internalsubstrate.

FIGS. 11A, 11B, 11C and 11D are cross-sectional views showingconfigurations of conductive components on the surfaces of an internalsubstrate.

FIG. 12 shows a press-fit pin.

FIG. 13 shows a magnified portion of FIG. 9A.

FIG. 14 shows an isometric view of an electronic module.

FIGS. 15 and 16 show isometric views of the module of FIG. 14 mounted toan external printed circuit board.

FIG. 17 shows an exploded isometric view of a configuration in whichexternal connections to an electronic module comprise ring lugs.

FIG. 18A shows a modified panel with cut lines after metallization.

FIG. 18B shows the panel of FIG. 18A after solder deposition.

FIGS. 19A and 19B show process flow charts for fabricating the modules.

Like reference numbers and symbols in the various drawings indicate likeelements.

DETAILED DESCRIPTION

An encapsulated electronic module, such as an electronic power convertermodule for example, may comprise a printed circuit assembly over-moldedwith an encapsulant to form some or all of the package and exteriorstructure or surfaces of the module. In the case of an electronic powerconverter module, the printed circuit assembly may include one or moreinductive components, such as inductors and transformers. Encapsulatedelectronic power converters capable of being surface mount soldered to acustomer motherboard are described in Vinciarelli et al., PowerConverter Package and Thermal Management, U.S. Pat. No. 7,361,844,issued Apr. 22, 2008, (the “SAC Package Patent”) (assigned to VLT, Inc.of Andover, Mass., the entire disclosure of which is incorporated hereinby reference). Encapsulated electronic modules having at least onesurface of a magnetic core structure exposed and methods formanufacturing the same are described in Vinciarelli et al.,Encapsulation Method and Apparatus for Electronic Modules, U.S. Pat. No.8,427,269 issued Apr. 23, 2013, (the “Exposed Core Patent”) (assigned toVI Chip Inc. of Andover, Mass., the entire disclosure of which isincorporated herein by reference). Methods of making encapsulatedmulti-cell power converters and interconnection modules are described inVinciarelli, Delivering Power to Semiconductor Loads, U.S. patentapplication Ser. No. 16/218,418, filed Dec. 12, 2018, (the “GearboxDisclosure”) (assigned to VLT, Inc. of Andover, Mass., the entiredisclosure of which is incorporated herein by reference).

Methods of over-molding both sides of a printed circuit board assemblywhile leaving opposing regions on both sides of the printed circuitboard free of encapsulant are described in Saxelby, et al., CircuitEncapsulation Process, U.S. Pat. No. 5,728,600, issued Mar. 17, 1998 andSaxelby, et al., Circuit Encapsulation, U.S. Pat. No. 6,403,009, issuedJun. 11, 2002 (collectively the “Molding Patents”) (both assigned toVLT, Inc. of Andover, Mass. and incorporated by reference in theirentirety).

Encapsulation of multiple electronic assemblies as panels followed bysingulation into individual modules and forming electrical contacts,e.g. “bar codes,” along vertical edges of individual modules, e.g.during singulation from the panel, for establishing electricalconnections to the circuitry inside each module are described inVinciarelli et al., Panel-Molded Electronic Assemblies, U.S. Pat. No.8,966,747, issued on Mar. 3, 2015 (the “Bar Code Patent”); and inVinciarelli et al., Panel-Molded Electronic Assemblies, U.S. Pat. No.9,402,319, issued on Jul. 26, 2016 (the “PM CIP”); enhancedthree-dimensional contacts for establishing robust solder connections tothe bar codes is described in Vinciarelli et al., Electronic AssembliesHaving Components With Edge Connectors, U.S. patent application Ser. No.14/596,914, filed on Jan. 14, 2015 (the “3D Bar Code Application”);encapsulation of multiple electronic assemblies as a panel, and formingelectrical contacts on multiple faces of each electronic assembly,including vertical and horizontal faces, prior to singulation of thepanel into modules, is described in Vinciarelli et al., Panel MoldedElectronic Assemblies With Multi-Surface Conductive Contacts, U.S.patent application Ser. No. 14/731,287, filed on Jun. 4, 2015 (the“Multi-Surface Application”); collectively the “Panel Mold Disclosures”(all of which are assigned to VLT, Inc. of Andover, Mass., and areincorporated in their entirety herein by reference). The Panel MoldDisclosures describe processes for making pluralities of electronicmodules in encapsulated panels, which may have interconnection featuresburied within the encapsulated panel, e.g. in a PCB encapsulated withinthe panel, and which are subsequently singulated into individualelectronic modules.

I. Terminal Inserts

Referring to FIG. 1, an electronic module 100 is shown having aplurality of electrical terminals, e.g. 130-1, 130-2, 140-1, 140-2, and170. The electric terminals can be made of, e.g., electricallyconductive metal. The electronic module includes a printed circuit board101 (“PCB”) (which can be, e.g., a multilayer printed circuit board)disposed between cured layers of encapsulant 102 and 103. The PCB 101may have electronic components, and conductive runs or traces and otherconductive features, mounted to its surfaces and enclosed within theencapsulant layers. The PCB 101 may have one or more conductive layersdisposed within the PCB 101, such that portions of the conductive layersare not exposed until holes are formed in the PCB 101 to expose theportions of the conductive layers. The terminals, which may extend into,but preferably not all the way through, the module 100 provide means formaking external connections to circuitry on the encapsulated PCB 101. Asshown in FIG. 1, relatively large electrical contacts, e.g. contacts130-1, 130-2, 140-1, 140-2 (each of which may include a threaded hole toreceive a threaded fastener, such as a screw, see, e.g. screws 970-1,970-2, 970-3, 970-4 in FIG. 17) provide relatively higher currentcarrying capacity, making them amenable for use as power connections. Inthe power converter example shown, contacts 140-1 and 140-2 may, e.g.,be used for input power connections, and contacts 130-1 and 130-2 may,e.g., be used for output power connections. A plurality of smallerterminals 170, having relatively smaller interconnect area and lowercurrent carrying capacity, may be provided for low current inputs oroutputs or for signal connections, such as control and communicationsignals.

Additionally, as shown in FIG. 1, portions of the outer surfaces of theencapsulant layers 102, 103 and the edges of PCB 101 (optionallyincluding areas covering magnetic cores (not shown), as described e.g.,in the Exposed Core patent), may be coated with an electrically (andthermally) conductive shield 150. The shield 150, which may, e.g. bemade of copper, may serve one or more functions, e.g. provide agrounding surface and/or an electromagnetic shield (e.g. for EMIreduction), improve heat distribution over the large surfaces of themodule (e.g. provide isothermal planes), improve thermal coupling to themodule (e.g. by conducting heat through a mounting board or substrate),and/or provide solder-mount options. Additionally, the plated conductivelayer may slow moisture absorption by the encapsulant (e.g., 102, 103),protect magnetic cores, and help control leakage inductance in internaltransformers.

The shield 150 may optionally make electrical connection to edges of thePCB along the perimeter of the module, i.e. along the cut lines, usingthe bar code techniques described in the Panel Mold Disclosures, e.g.using the techniques described in the Multi-Surface Application.However, the shield may instead, or additionally, be electricallyconnected to conductive traces in the PCB 101 via the apertures 160-1,160-2, 160-3, 160-4, using the process described below. Of course, theelectrical shield 150 need not make electrical connection to internalcircuitry, or to the PCB 101 at all, remaining electrically isolated. Asalso shown in FIG. 1, the module 100 may comprise apertures, e.g.apertures 160-1, 160-2, 160-3, 160-4, which may preferably extend allthe way through the module, which may for example provide holes formounting the module to a larger assembly. The apertures 160-1, 160-2,160-3, and 160-4 may additionally be used for electrical connections,e.g. a ground or common terminal, and facilitate heat removal bymounting the module to a cold plate, heat sink, or other heat removaldevice.

A. Panel Preparation

A process for making the electronic modules 100, illustrated in FIGS. 3through 6 builds upon the panel molding processes described in the PanelMold Disclosures focusing on making terminals 130, 140, 170 andapertures 160. In the example of FIGS. 3-6, the encapsulated panel 190comprises four un-singulated electronic modules 100A, 100B, 100C, 100D,which when finished will include a conductive shield 150 connected tothe edges of the PCB 101. Note that the electrical terminals, e.g.130-1, 130-2, 140-1, 140-2, and 170 (FIG. 1) may be formed in module 100with or without the optional electrical connections, e.g. to the shield150, to the edges of the PCB 101 along the cut lines.

The following process description starts from just after the PCB panelis encapsulated as described in the Multi-Surface Application. Theencapsulated panel 190 which is partially shown in the example of FIGS.3 through 6 comprises four un-singulated electronic modules. (See also,encapsulated panel 890 shown in FIGS. 43-44 of the PM CIP and panel102-1 in FIGS. 4-9 of the Multi-Surface Application.) Note that thepanels in the Panel Mold Disclosures (which are assumed to be the samesize as in the present example) are shown comprising a larger number ofun-singulated electronic modules 100, reflecting the dependency onmodule size, e.g. the relatively larger modules 100 in FIGS. 3-6,results in fewer modules per panel.

As shown in FIG. 3, the panel 190 is shown with several cut lines 191through 198 representing the edges of a plurality of un-singulatedmodules, 100A, 100B, 100C, 100D: cut lines 191, 192, 193, 194representing boundaries between adjacent modules and cut lines 195, 196,197, and 198 representing the boundaries between modules and scrapmaterial. Electronic components and conductive features associated witheach module are included within the respective cut lines defining theboundaries of the module. The modules 100A-100D remain integral parts ofthe encapsulated panel 190 until separated from the panel by singulationcuts. Also shown in FIG. 3 are exposed, e.g. non-encapsulated, arease.g. features 180-1, 180-2, 180-3, 180-4, 180-5, of the surface of PCB101 that may be provided to locate reference holes or fiducials foralignment or identification of the panel during manufacture. (See col.30, ln. 24-col. 30, ln. 46 in the PM CIP).

Holes, including blind holes and through holes, may be formed in theencapsulated panel 190 to establish the locations of the terminals andapertures. (As used herein, a blind hole refers to a hole that extendspartially into, but not completely through, the panel; and a throughhole refers to a hole that extends completely through the panel.) Forexample, FIG. 3 shows blind holes 136-1, 136-2, 146-1, 146-2 and 176(e.g. 176-1, 176-2, 176-3, 176-4, 176-5) and through holes 160-1, 160-2,160-3 and 160-4 formed in un-singulated module 100A, corresponding tothe locations of terminals 130-1, 130-2, 140-1, 140-2 and 170 (i.e.170-1, 170-2, 170-3, 170-4, 170-5) and apertures 160-1, 160-2, 160-3 and160-4 shown in FIG. 1. Corresponding holes (not labeled) are shownformed at corresponding locations on the other modules 100B, 100C, 100Don the panel 190. The mounting holes, e.g. 160-1, 160-2, 160-3, 160-4,preferably may be formed as through holes, which extend completelythrough the module, allow mounting hardware to pass through the module;while the holes, e.g. 136-1, 136-2, 146-1, 146-2 and 176, for theterminals, e.g. 130-1, 130-2, 140-1, 140-2 and 170 (i.e. 170-1, 170-2,170-3, 170-4, 170-5), may be blind holes providing electrical isolationbetween each terminal and the shielding or mounting surfaces on theopposite side of the module, e.g. chassis, cold plate, heat sink orother heat removal structure without the need for added insulation.

Holes 136-1, 136-2, 146-1, 146-2 and 176 (for the terminals) each maytherefore be preferably formed to extend partially through the thicknessof the module to expose conductive features buried within the module formaking electrical connections from one side of the module, but notextend so far as would require insulation on the opposite side; and morepreferably, extend only as deep as required to expose the conductivefeatures necessary for each terminal. Referring to FIG. 7A, which showsa cross-section though module 100A at the center of blind hole 136-2,shows the depth of the blind hole, D₁, (FIG. 7A) extending all the waythrough encapsulant layer 103, all the way through PCB 101, and into butnot through, e.g. part of the way through, encapsulation layer 102, i.e.the depth, D₁, is less than the thickness, T of the module. As shownblind hole 136-2 is preferably formed to expose conductive featuresburied in the module. As shown in FIG. 7A, the hole may be formed topass through the conductive features, e.g. conductive features 200-1,200-2, 200-3, 200-4, representing traces in layers of the multilayer PCB101, exposing one or more layers of conductive traces on the innersurfaces (e.g. surfaces 210-1, 210-2) of the hole 136-2. As shown inFIG. 7A, the hole passes through conductive traces located in more thanone of the conductive PCB layers producing conductive rings in the wallof the hole 136-2, akin to the bar code terminations described in the PMCIP, Bar Code Patent, and Multi-Surface Application.

A more detailed description of buried interconnects and bar codes may befound in the PM CIP at col. 17, ln. 36-col. 19, ln. 14, in the Bar CodePatent at col. 15, ln. 40-col. 17, ln. 2; and at paragraphs 036 and 037of the Multi-Surface Application. The bar codes described in the PM CIP,Bar Code Patent, and Multi-Surface Application may be formed primarilyalong module boundaries and exposed during singulation in the PM CIP andBar Code Patent or before singulation in the Multi-Surface Application.The bar codes in the Multi-Surface Application are exposed in a similarfashion, e.g. by forming holes to expose the buried conductive features;however, the process in the present disclosure forms the holes andexposes the conductive features in areas of the module that may notinclude the cut lines, i.e. are located completely within the boundariesof each individual module, rather than along the boundary, andpreferably result in one or more conductive rings in the side walls ofthe holes (which are undisturbed by singulation). The conductivefeatures exposed by forming the holes may preferably result inconductive rings embedded in the inner surface of the holes, however,they need not. For example, the conductive rings are formed when thehole passes through a horizontal conductive layer that completelysurrounds the hole. For conductive features that are not horizontalrelative to the vertical axis of the hole or that may not completelysurround the hole, the shape of the conductive feature exposed in theinner surface of the hole, i.e. the hole wall, may differ. For example,a hole may pass through only a portion of a conductive feature such as apuck on the surface of, or a conductive layer in, the PCB 101, so theconductive feature may not be present in the entire circumference of thehole, thus not appearing as a ring. For simplicity the followingdescription will refer to the conductive features exposed in the holesas “conductive rings” consistent with the embodiment having holes thatpenetrate the PCB, but the term should be understood to refer generallyto any conductive feature exposed by forming the hole. For example, theconductive rings can have a circular shape, an elliptical shape, a starshape, or any other shape of the hole. The conductive rings may notcompletely surround the hole and may not be horizontal relative to thevertical axis of the hole. In some examples, the conductive featuresexposed in the holes are considered to be edges of the conductivelayers. In the case of a conductive puck on a surface of the PCB, theexposed feature may appear as a single conductive sleeve in the hole.

The cross section through the centers of blind holes 176 in FIG. 7C,shows the depth, D₂, of the holes 176 relative to the PCB 101 andencapsulation layers 102, 103. As shown blind holes 176 extendcompletely through encapsulant layer 103, partially into but notcompletely through PCB 101, and not at all into encapsulation layer 102.Controlling the depth, e.g. depth D₂, during formation of the blindholes, e.g. holes 176, allows selective exposure of buried conductivefeatures, e.g. conductive PCB traces exposed as one or more conductiverings on the inner surface of the hole and greater utilization of otherlayers of the PCB. For example, conductive traces 200-6, 200-7, 200-8and 200-9 are shown exposed in blind hole 176-3 while conductive traces200-10, 200-11 are not exposed in FIG. 7C.

Alternatively, blind holes may be formed to avoid penetrating theinternal substrate in the panel. Referring to FIG. 7B, the depth, D3, ofthe holes, e.g. hole 136-2B, is shown avoiding penetration of the PCB101. As shown, hole 136-2B extends to the surface of the PCB 101, whichin the example shown, exposes a conductive feature 200-5 at the bottomof the hole. In this variation, the conductive feature may appear as anessentially flat conductive surface at the bottom of the hole having aperimeter that essentially matches that of the hole. For convenience,the term “conductive plate” will be used herein to refer to theconductive features 210-5 exposed at the bottom of blind holes that donot penetrate the PCB 101 irrespective of the shape of the hole. A lasermay be particularly adept at forming holes of the type shown in FIG. 7B,where the wavelength of the laser may be chosen to selectively removethe encapsulant, e.g. encapsulant 103, at an efficient rate, but doesnot significantly remove conductive features, e.g. copper traces on thesurface of the PCB 101, or conductive features mounted to the surface ofthe PCB 101, in which case the conductive feature to be exposed may beused to control the depth of the hole. For example, the laser wavelengthmay be chosen to provide a removal rate of encapsulant that is one ormore orders of magnitude greater than the removal rate of copper. Laserdrilling may be preferable over mechanical drilling for the precision ofthe hole depth which may be controlled by the conductive feature.Additionally non-circular holes may be more easily formed with the lasercompared to a mechanical drill or router. For example, oval slots andother hole shapes are easily formed with the laser, e.g. non-circularholes may provide venting during soldering, e.g. allowing use of simplerterminals, i.e. without ridges along the shank, to save cost, and mayresist rotation of the terminals, i.e. to provide improved mechanicalintegrity; or be shaped to facilitate plating processes, e.g. to improvemetal deposition in the holes.

Optionally, electrically conductive features may be mounted to the PCB101, e.g. on one or both surfaces of the PCB 101, remain buried withinthe encapsulated panel, and exposed by forming the holes 176; with theadvantage of increasing the exposed area of the conductive rings forholes that penetrate the conductive feature or the performance of theconductive plate or to provide a buffer for laser drilled holes in theFIG. 7B variation.

By limiting the depth, D, of holes to be less than the thickness, T, ofthe module (e.g., D₁<T, D₂<T, D₃<T) no part of the terminals (e.g.terminals 130) are exposed at the outer surface of encapsulation layer102. This may provide enhanced insulation and safety and make the outersurfaces of layer 102 adjacent to the holes available for plating withshields or other conductive patterns. Partial depth holes may alsoresult in better mechanical support for terminals.

Optionally, electrical connections to the PCB 101 along the perimeter ofthe individual modules, e.g. module 100 (FIG. 1) may be establishedusing the process descried in the Multi-Surface Application. Forexample, the shield 150 shown in FIG. 1 may be electrically connected tothe PCB along one or more of the four edges of the module using theMulti-Surface process. Accordingly in FIG. 4, panel 190 (which comprisesfour un-singulated electronic modules) is shown having optional slots,e.g. slots 221 through 228, formed in the panel, e.g. cut all the waythrough the panel as described in the Multi-Surface Application, alongthe cut lines 191-198 to establish electrical connections at the edgesof the PCB 101. Cutting of slots of this kind may be done using, e.g. awater jet as described in the Multi-Surface Application at paragraph 38.The connections formed along the module perimeter, via the slots, may beused in addition to electrical connections formed via the holes 160,e.g. to improve electrical performance. Of course, connections along theperimeter of the module may be omitted in which case forming the slotsbefore plating also may be omitted.

FIG. 5 shows the panel 190 after a conductive layer has been formed,e.g. by plating, on selected surfaces of the module, including thesurfaces within slots 221 through 228, and patterned as described in theMulti-Surface Application. The conductive layer 150 in FIG. 5,corresponding to conductive shield 150 in FIG. 1, may as shown provide acontinuous conductive shield covering the outer surfaces of theencapsulant layers 102, 103 and the sides of the modules exposed withinthe slots 221, 223, 226. Alternatively, the shield may be patterned tocover select portions of the surfaces as desired, e.g. the shield 150may preferably cover at least 25 percent, or 50 percent or more of themodule surfaces.

Preferably, the process of forming the conductive layer depositsconductive material inside of the exposed holes and optional slots, e.g.blind holes 136-1, 135-2, 146-1, 146-2 and 176, through-holes 160-1,160-2, 160-3 and 160-4; and on the exposed surfaces of the panel, e.g.in regions 231, 232, 233, and 234 on the module surface, adjacent to theholes providing a conductive layer around each hole, i.e. a conductivepad. Plating within the holes may form a conductive connection to theconductive bar code pattern(s) or conductive plate(s) on the innersurfaces of the holes and slots. A variety of processes for providingconductive material on panel surfaces and in the slots and holes, e.g.using plating processes which may include masking, deposition of a seedlayer, and electroless or electrolytic plating of copper, are describedin paragraphs 40-48 in the Multi-Surface Application. As shown, theconductive layer is patterned to provide conductive material on thesurface surrounding each hole that preferably extends into the holemaking electrical contact with the exposed conductive features, e.g.conductive rings or conductive plate in the hole. The through-holes,160-1, 160-2, 160-3 and 160-4, in the example of FIG. 5 may be formed,as shown, in the area in which the conductive shield is to be formed,and the conductive layers formed on the exposed interior surfaces of thethrough-holes can be connected to the conductive shield, which mayadditionally be connected to either bar codes along the module perimeteredge as shown, conductive rings within each through-hole, or both.Alternatively, one or more through holes may be electrically isolatedfrom the shield by appropriate patterning of the shield in the mannershown for the blind-holes 136 in FIG. 5.

FIG. 6 shows a portion of the panel 190 after the singulation cuts havebeen made, dividing the panel into individual modules. Singulationmethods, which may include cutting along cut lines (e.g. cut lines191-198, FIG. 3) within the slots (e.g. slots 221-228, FIGS. 4 and 5)using a thin saw, e.g. 0.012″ blade, are described at col. 17, lns.7-34, in the PM CIP and paragraph 49 in the Multi-Surface Application.Because the plating step provided plating within the slots, a continuousshield 150 may be formed on multiple surfaces of the modules, as shownin FIGS. 1 and 6. Exposing bar codes along the perimeter edge of themodule for making electrical connection to the conductive shield, whichis not necessary for the present embodiment, may be supplanted oraugmented with connections formed within the through-holes. For example,the slots along the perimeter edges of the modules (e.g. slots 221-228,FIGS. 4 and 5) may be omitted completely, in which case the conductiveshield may be absent from the vertical edges of the singulated modulesand may be patterned to include a setback from the vertical edges ifdesired.

B. Terminal Assembly

The terminals may be assembled to the module before or aftersingulation, each approach having its own advantages and disadvantages.For example, terminal assembly before singulation may be advantageousfor standardized panel handling equipment but would present cleaningchallenges following singulation. Conversely, terminal assemblyfollowing singulation avoids subjecting the terminals to singulationresidue in the terminals which may be preferable even with potentialmodule-specific assembly challenges. Referring to FIG. 2, an explodedview of a module 100 is shown with terminals 130-1, 130-2, 140-1, 140-2and 170 prior to insertion into and assembly with their respectiveplated holes 236-1, 236-2, 246-1, 246-2 and 276. Terminals may besecured within their respective holes in a variety of ways, including,e.g., soldering or press-fitting, and the configuration of the portionof a terminal that is inserted into a hole may be adapted as desiredaccording to the function, configuration and size of the terminal andthe method of insertion.

Referring to FIG. 8A which shows a detailed cross-sectional view ofterminal 130-2 assembled with a respective PCB-penetrating plated hole236-2 (FIGS. 7A, 7C). As shown, conductive plating 237 on the insidesurface of the hole 236-2 is electrically connected to the conductiverings, i.e. the exposed conductive layers of PCB 101 (e.g. conductivelayers 200-1 through 200-4). As shown, the region between the interiorplated surface of the plated hole 236-2 and the exterior surface of theterminal 130-2 within the hole may be filled with solder 250 to form arobust electrical and mechanical connection. To allow gases to escapefrom the hole during the soldering process, the terminal 130-2 mayinclude contours to provide clearance between the terminal 130-2 and theinterior surface of the hole (e.g. dimension W, FIG. 8A). For example,FIG. 2 shows terminals 130-1, 130-2, 140-1, 140-2, having anapproximately octagonal shape, which provides gaps between the flatsurfaces 270 of the terminal and the circular walls of the hole. Othercontours, shapes, or indentations may be provided to allow gases toescape from the holes during soldering.

Referring to FIG. 8B, a cross-sectional view of terminal 130-2 assembledwith a respective non-PCB penetrating plated hole 236-2B is shown withconductive plating 237 on the inside surface of the hole 236-2B. Theconductive plating 237 in the embodiment shown in FIG. 8B iselectrically connected to the exposed metal layer on the surface of thePCB 101, i.e. the exposed top conductive layer of PCB 101 (e.g.conductive layer 200-5). Similar to the embodiment of FIG. 8A, theregion between the surface of conductive layer 237 in the plated hole236-2B and the exterior surface of the terminal 130-2 within the holemay be filled with solder 250 to form a robust electrical and mechanicalconnection. Gases may be allowed to escape from the hole duringsoldering in the clearance between the terminal 130-2 and the interiorsurface of the hole (e.g. dimension W, FIG. 8B) which may be providedusing differences in shape between the hole and the terminal 130-2.

At first glance, comparison of FIGS. 8A and 8B, may suggest a currentcarrying advantage in FIG. 8A which inherently allows the currentthrough the terminal to flow through a plurality of the PCB layers vs asingle layer in FIG. 8B. However, the surface area of the exposedconductive feature 210-5 making contact with the conductive layer(s) 237in the hole in FIG. 8B may be much greater than the embodiment on FIG.8A (depending on the number and thickness of exposed layers and thesurface area of the hole) and limitations on the number and placement ofconductive vias that may be distributed, e.g. within and around, eachhole may be negligible in the embodiment of FIG. 8B compared with FIG.8A because wear on a mechanical drill bit is not a concern with thelaser formed holes. Thus, in the embodiment of FIG. 8B, with a laserdrill, a plurality of conductive vias may be distributed in and aroundthe area of the hole 136-2B to connect to a plurality of conductivelayers for a more robust electrical and thermal connection.

The cross-sectional views of FIGS. 9A and 9B show terminals 130-1, 130-2and 170-3 soldered into their respective PCB-penetrating plated holes236-1, 236-2, 176-3 (FIG. 9A) and non-PCB-penetrating holes 236-1B,236-2B, 176-3B (FIG. 9B) and four terminals 170-1, 170-2, 170-4, 170-5which may be press-fit within their respective PCB-penetrating platedholes 176-1, 176-2, 176-4, 176-5 (FIG. 9A) and non-PCB-penetratingplated holes 176-1B, 176-2B, 176-4B, 176-5B (FIG. 9B) as describedbelow.

In some embodiments, one or more conductive components, e.g. conductivepucks 300 (FIGS. 10, 11), may be mounted on a surface, or surfaces, ofthe PCB 101 prior to encapsulation in locations that enable theconductive component to be exposed by the formation of a terminal hole.FIG. 10, which shows an isometric view of a module with the top layer ofencapsulant removed, provides another example of a conductive component300 arranged on the surface of PCB 101. The conductive component 300may, e.g. be a copper plate or bar as shown or may have any suitableshape for the application. The dashed line 400 in FIG. 10 shows alocation where a terminal hole may subsequently be formed. As shown, ahole 410 may be optionally provided in the conductive component near theintended terminal hole 400, e.g., to minimize wear on equipment, e.g. adrill, used to form the terminal hole, or decrease the process time forforming the hole, e.g. because of less metal requiring removal.Preferably, the hole 410 would be located, e.g. completely within, theintended terminal hole 400, to allow the formation of the latter tocompletely define the portion of the conductive component that issubsequently exposed in the terminal hole, providing improved accuracyand ensuring the terminal pin adequately engages the conductivecomponent. In embodiments in which the terminal hole does not penetratethe PCB 101, the hole 410 may be omitted.

FIGS. 11A, 11B, 11C and 11D show several examples of alternateconfigurations using conductive components on one or more of the PCBsurfaces. In FIG. 11A the conductive component 300 is placed on a topsurface of the PCB 101 in contact with conductive trace 205, so that theplated terminal hole 236 passes through it. The plating 237 in the holeconnects to exposed conductive rings 200-1 through 200-4 in the hole andto the conductive component 300. FIG. 11B shows a configuration in whichthe terminal hole 236 passes through conductive components 300 a, 205 a,205 b, 300 b that are located on both top and bottom surfaces of the PCB101. FIG. 11C shows a configuration in which the bottom of the terminalhole 236 contacts the conductive component on the surface of PCB 101.FIG. 11D shows a configuration in which the bottom of thenon-PCB-penetrating terminal hole 236 contacts the conductive component300 on the surface of PCB 101. A conductive component may be locatedover, and may be soldered to, a conductive trace on the PCB at thelocation of the terminal hole (e.g. conductive traces 205, 205 a, 205b); it may be placed over bare portions of the surface of the PCB 101 atthe location of the terminal hole and be connected at another locationto circuitry on the PCB 101 (i.e. a bus bar); or it may be placed on abare portion of the PCB only (i.e. for mechanical support). The examplesof FIG. 11A through 11D are illustrative; it is understood that thereare many possible configurations of conductive components and terminalholes. By providing additional cross-sectional area in the conductionpath, the conductive component may reduce the equivalent seriesresistance of a terminal. It may also provide increased mechanicalstrength and rigidity.

An example of press-fit pin terminals will be described with referenceto FIGS. 12 and 13, which respectively show a press-fit pin 170; and amagnified view of a portion of FIG. 9A that includes pins 170-1, 170-2,170-3, 170-4, 170-5. As shown in FIG. 13, an optional conductivecomponent, e.g. “puck” 260, is soldered or otherwise electricallyconnected to a respective conductive trace or pad (e.g. pad 220) on PCB101 for each of pins 170-1, 170-2, 170-4, 170-5 in the pin's respectivelocation. Each puck is preferably made of a malleable electricallyconductive material, e.g. copper, may form a substantial part of theelectrical connection between the pin and the respective PCB trace, andprovide mechanical support for the press-fit pin. The conductivefeatures, e.g. puck 260, may be buried by the encapsulation process,after which, each puck may be exposed by formation of a respective hole,e.g. PCB-penetrating holes 176-1, 176-2, 176-3, 176-4, 176-5, e.g.drilled. Each hole may pass through encapsulant layer 103 and, in theexample shown, through the respective puck 260 and optionally throughall, or preferably only a portion of, PCB 101. As indicated in FIG. 13,the hole preferably may be formed to have a diameter X of an upperportion that is larger than a diameter Y of a lower portion (e.g. by useof two drill bits or a single stepped drill bit, etc.). The press-fitpin 170, shown prior in FIG. 12, may have a lower portion 178 that islarger in diameter than an upper portion 179 (i.e., in FIG. 12, diameterB is greater than diameter T). The diameter B of the pin lower portion178 may be greater than the diameter, Y, of the lower portion of hole176-2, but preferably less than the diameter X of the upper portion ofhole 176-2 to facilitate compression of the lower portion of the pin 178by the smaller internal diameter of the puck 260 when pin 170-2 ispressed into hole 176-2. This frictional compressive fit may secure thepin mechanically and may also ensure a low resistance, high quality,electrical connection between the pin and the conductive puck. In someapplications, adhesive may be placed between the head of pin 170 and thesurface of encapsulant layer 103 (e.g. at location 285, FIG. 13).Alternatively, the press-fit pins 170 may engage with the sidewall ofthe holes without the use of conductive pucks mounted to the PCB, e.g.directly with either the PCB or with the metalized holes.

It should be appreciated that plating inside of one or more ofthrough-holes 160-1, 160-2, 160-3, 160-4 (FIGS. 1, 3, 5) may connect tocircuitry on the PCB 101, e.g. connecting the shield 150 to internalcircuitry within the module, e.g., to a circuit ground. Similarly, theplating inside the one or more blind-holes, e.g. holes 136-1, 136-2,146-1, 146-2, 176-1, 176-2, 176-3, 176-4, 176-5, may selectively connectto portions of the internal circuitry providing electrical terminals,such as power input, power output, and control signals in the case of apower converter.

A wide variety of terminal and mounting configurations are possible.FIG. 14, for example, shows a module 100 having terminals 530-1, 530-2,540-1, 540-2 comprising columnar studs that extend beyond a surface ofthe module and that may be used to connect the module, as illustrated inFIGS. 15 and 16, to an external printed circuit board 600 or connectors.In FIGS. 15 and 16, the module 100 is secured to the external PCB 600 bymeans of screws 960-1 through 960-4, which pass through through-holes160-1 through 160-4, and threaded nuts or inserts 980-1 through 980-4.Columnar studs on terminals 530-1, 530-2, 540-1, 540-2 pass throughholes in external PCB 600 and may be soldered to etches (not shown) onthe external PCB or alternatively may engage with connectors (notshown). FIG. 17 shows an exploded view of another configuration in whichring lugs 730-1, 730-2, 740-1, 740-2 are secured to respectiveinternally threaded terminals 130-1, 130-2, 140-1, 140-2 by means ofscrews 970-1 through 970-4. In FIG. 17, mounting screws 960-1 through960-4 may be inserted into through-holes 160-1 through 160-4 to securethe module to, e.g. an external chassis or heat sink assembly (notshown). It should be appreciated that a wide variety of terminal shapesand sizes may be used. For example, terminals may be inserted into theholes that may be sized, cut, or ground to be coplanar with the surfaceof the finished module, or extend slightly above or below the modulesurface to provide connection bumps, or indentations.

II. Surface Mount Trench Terminals

An alternative “trench” type terminal may be used without the terminalinserts, e.g. inserts 130-1, 140-1, (FIGS. 1-2, 8-9), inserts 530-1540-1 (FIG. 14), pins 170-1, 170-3 (FIGS. 1-2, 12-13) described above.Referring to FIGS. 18A and 18B, which partially show encapsulated panels190-2, comprising a large multiplicity of un-singulated electronicmodules, e.g. 100-2A, 100-2C, each having a plurality of electricaltrench terminals, e.g. terminals 137A, 137B, 137C, 137D (FIG. 18A). Theexample of FIGS. 18A and 18B assumes panels 190-2 of the same size, andun-singulated modules, e.g. 100-2A, 100-2B, 100-2C, 100-2D, 100-2E,100-2F, of a size much smaller than, those (panels 190, un-singulatedmodules 100) in the previous examples of FIGS. 1-6 and 14-17. Theun-singulated modules, 100-2, may be delineated by cut lines 191, whichin contrast to the example of FIGS. 1-6, do not pass through anymetalized slots or holes as shown in FIGS. 18A, 18B, i.e. the perimetercontacts described in the Multi-Surface Application are not employed inthis example. The trench terminals 137A, 137B, 137C, 137D as shown inFIG. 18A are unfilled plated holes (see Insert 18A for a magnified viewof an unfilled plated hole) in contrast to the trench terminals 138A,138B, 138C, 138D shown in FIG. 18B as filled (see Insert 18B for amagnified view of a filled plated hole). The plated holes may be filledpartially or completely with a curable compound, e.g. epoxy, preferablyconductive, to leave a controlled volume of the trench unfilled, e.g.the controlled volume may range from 0 to 100 percent unfilled, forsubsequent solder deposition or additional plating onto the curedcompound in the trench or hole. Alternatively, the trench terminals maybe filled partially or completely during the plating process, e.g., byplating, leaving a dimple or approximately flat pad, in or on whichsolder paste may optionally be deposited.

The metal formed on a surface of the modules 100-2 may be patterned asnecessary for the application, e.g. in FIGS. 18A, 18B the metal on thetop surface is shown patterned into strips, e.g. metal strips 232-1A,232-1B, and 232-1C, for a power converter application. Each strip232-1A, 232-1B, and 232-1C, may include a plurality of trenches, 137B,137C, and 137D, respectively providing a plurality of connections toeach metal strip, for example to provide high current connections, asshown in FIG. 18A. One or more additional trench terminals 137A may beisolated from the metal strips 232-1A, 232-1B, 232-1C to provide lowercurrent signal connections, e.g. timing and control signals, to themodule, e.g. at an end of each module as shown in the example of FIGS.18A and 18B. Typically, one surface of the module may be dedicated forelectrical connections to the system in which it is installed, e.g.surface mounted, and the opposite surface may be use for shielding andor heat removal, e.g. attached to a heatsink or cold plate, in whichcase the metal may cover the entire opposite surface with or without asetback from the edges of the module, e.g. cut lines 191. The metal onthe opposite surface, e.g. the shield, may also include trench terminalsof the type shown in FIGS. 18A and 18B. The trenches in the surface ofthe panel may be partially or completely filled, e.g. with one or morefillers to form the terminals, e.g. the trenches may be partially filledwith a curable compound such as an epoxy and then filled with solderpaste for subsequent attachment to a system board or other device. Forexample, the curable compound may be cured before filling or partiallyfilling the trenches with the solder paste.

III. Fabrication Process Flow

The processes for fabricating the above modules using insert terminalsor trench terminals are summarized in the flow charts 610 and 620 ofFIGS. 19A and 19B. The process 610 in FIG. 19A illustrates the preferredsingulate before terminal assembly method described above for buildingmodules with terminal inserts. The PCB panels may be assembled as shownin step 601, e.g. attaching the various components to the PCB; theassembled panels being encapsulated in step 602, and the encapsulatedpanels being lapped in step 603, e.g. for thickness and planaritycontrol. The terminal holes, e.g. blind holes 176, 136, and 146 (FIG.3), through holes 160 (FIG. 3), and optional slots 221, 225, 226 (FIG.4) may be formed, preferably using a laser to remove the encapsulant toa controlled depth, preferably to the first metal layer on the PCB forthe blind holes, and then panels may be cleaned as shown in step 604.The panels may be metalized as shown in step 605, which may includeforming metal inside the holes and optional slots, and may includeadditive or subtractive patterning to form the requisite pattern, e.g.metal shield, clearance between terminal holes and shield, andconductive features on the surface around the terminal holes, e.g. inregions 231, 232, 233, 234 (FIGS. 5-6) on the surfaces of the panels asdescribed above. The panel may be cut to singulate the individualmodules which may then be cleaned as shown in step 606A; after whichsolder may be dispensed to the blind terminal holes as shown in step607A. The terminals may be inserted into their respective holes as shownin step 608A and the solder reflowed as shown in step 609A to completethe process.

The singulate and clean step 606A of process 610 may be moved to the endafter the reflow step 609A should the terminal assembly before singulateprocess be preferred.

It will be appreciated that any size or shape solder terminals may beprovided according to the needs of the application. Finally, the panelsmay be cut along the cut lines, e.g. lines 191-198 in FIG. 3, tosingulate the individual modules, e.g. modules 100A, 100B (FIG. 3).

The trenches for the trench terminals may be formed using the sametechniques described above for holes 136-2B in FIG. 7B. For example, theprocess for making the trench terminals may start from just after thePCB panel is encapsulated as described in the Multi-Surface Applicationand may preferably use non-PCB-penetrating holes similar to thosedescribed above in connection with FIG. 7B, however, the size of theholes for forming the trench terminals is preferably much smaller thanthose described above for the terminal inserts, and may preferably havenon-circular geometries, e.g. length to width aspect ratios that allowsfor effecting metal plating in the holes, all making them particularlyamenable to formation by laser drilling. As shown in FIG. 18A, thetrench holes 137A, 137B, 137C, and 137D, may be oval slots for example.Slots may be preferable to round holes for small hole dimensions toallow the inner walls of the slot to be plated during subsequent metallayer formation.

The process 620 for fabricating the trench terminals is summarized inFIG. 19B, which shows the PCB panels being assembled in step 601, theassembled panels being encapsulated in step 602, the encapsulated panelsbeing lapped in step 603, e.g. for thickness and planarity control, andthen the trenches, e.g. slots, are formed, preferably using a laser toremove the encapsulant to a controlled depth, preferably to the firstmetal layer on the PCB and the panels cleaned in step 604, and thenmetalized in step 605, which includes forming metal inside the trenchesor slots, and may include additive or subtractive patterning to form therequisite conductive features, e.g. metal strips, signal terminals, andshields on the surfaces of the panels as described above. The slots mayoptionally be substantially filled with metal by the plating process, oralternatively filled afterward with a curable compound, which maypreferably be conductive as shown in step 606B. Solder may be dispensedto the filled or unfilled slots as shown for step 607B and then may beoptionally planarized, e.g. by applying a compressive force, to acontrolled height, e.g. a uniform height for the dispensed solder asshown in step 608B. Finally, the panels may be cut along the cut lines,e.g. lines 191 in FIGS. 18A and 18B, to singulate the individualmodules, e.g. modules 100-2A, 100-2B (FIGS. 18A and 18B).

Several embodiments of the invention have been described. Nevertheless,it will be understood that various modifications may be made withoutdeparting from the spirit and scope of the invention. For example, itwill be appreciated that any size or shape terminal or trench may beprovided according to the needs of the application. Although acontinuous shield 150 has been shown above as an example of plating onthe surface of a module, the plating may be configured in a virtuallylimitless number of ways, including forming electrical contacts on theoutside of the module that enable connecting internal module circuitryto external components or other modules. Examples of “bar code” etchesshown herein were limited, for clarity of illustration, to relativelyfew layers on the internal PCB. The number of layers in a particularembodiment is a function of the application and may be relatively small(e.g. 2 layers, 5 layers) or relatively large (e.g., 11 layers, 30layers).

Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A method of forming electronic modules, themethod comprising: assembling an electronic module including amultilayer printed circuit board (“PCB”) having a plurality ofconductive layers, a first plurality of electronic components mounted toa first surface of the PCB, and a first layer of cured encapsulantcovering the components and the surface of the PCB, the first layer ofcured encapsulant forming a first exterior surface of the module, theelectronic module including one or more conductive features buriedbeneath the first exterior surface; selectively forming one or moreterminal holes in the first exterior surface through the first layer byremoving the cured encapsulant at predetermined locations withinperimeter boundaries of the electronic module, exposing within the oneor more terminal holes respective portions of the one or more conductivefeatures; inserting a conductive terminal into each of the one or moreterminal holes; and forming an electrical connection between theconductive terminal and the respective portions of the one or moreconductive features exposed within each of the one or more terminalholes; wherein assembling the electronic module comprises providing aPCB panel, mounting a plurality of electronic components to first andsecond surfaces of the PCB panel, encapsulating the PCB panel andelectronic components to form an encapsulated panel, the encapsulatedpanel comprising a plurality of the electronic modules, and cutting theencapsulated panel to singulate the electronic modules.
 2. The method ofclaim 1 wherein the forming an electrical connection for selectedterminal holes includes forming a pressure fit between the respectiveconductive terminal and the respective portions of the one or moreconductive features exposed within the selected terminal holes.
 3. Themethod of claim 1 wherein the assembling the electronic module includesmounting at least one conductive component to the PCB, the at least oneconductive component being covered by the first layer of curedencapsulant, and wherein forming the one or more terminal holes includesexposing the conductive component in a respective one of the terminalholes.
 4. The method of claim 3 wherein the conductive componentincludes a hole feature covered by the first layer of cured encapsulantand approximately aligned with a location of the respective one of theterminal holes, and the forming the respective one of the terminal holesexposes the hole feature.
 5. The method of claim 1, further comprisingselectively forming one or more conductive metal layers on a sidewallsurface within each of selected terminal holes in electrical contactwith the respective portions of the one or more conductive featuresexposed within the selected terminal holes.
 6. The method of claim 1,further comprising: selectively forming one or more mounting holes inthe first exterior surface through the first layer at predeterminedlocations within perimeter boundaries of the electronic module, eachmounting hole intersecting a respective second set of the conductivefeatures to expose respective portions of the respective second set ofconductive features in the respective mounting hole; and selectivelyforming one or more conductive metal layers on the first externalsurface and on a sidewall surface within each of selected mounting holesin electrical contact with the exposed respective portions of therespective second set of conductive features in the respective mountinghole to form a conductive metal mounting pad on the first exteriorsurface surrounding the respective mounting hole, the metal mounting padbeing continuous with the one or more conductive metal layers on theinterior surface of the respective mounting hole and providing anelectrical contact on the first exterior surface connected to theexposed respective portions of the respective second set of theconductive features.
 7. The method of claim 6, further comprisingpatterning the one or more metal layers on the first exterior surface toform a metal shield electrically connected to at least one of the metalmounting pads and covering at least 25 percent of the first exteriorsurface.
 8. The method of claim 7 wherein the metal shield covers atleast 50 percent of the exterior module surface and connects a pluralityof the mounting holes.
 9. The method of claim 6 wherein at least one ofthe mounting holes extends completely through the module.